Water is a critical natural resource for which demand is high. In addition to clean water for consumption, there is a need for the conservation of water as demand on available resources continues to grow. As such, products which contribute to the recycling and conservation of water resources are desirable to certain consumers and may be required by legislation.
The washing machine is an appliance that is commonly found in residential and commercial settings and which typically uses water to properly clean articles such as e.g., clothes, linens, towels, and other machine washable items. A detergent, generally one that contains surfactants and possibly brighteners as well, is added to the water for cleaning. A fabric softener may be used during a rinse cycle for purposes of softening the washed articles, controlling static cling, and adding a scent to the articles. For certain applications, it can be desirable to recycle the water effluent from a washing machine. More particularly, water from the wash cycle, rinse cycle, or combinations thereof can be recycled by using such water again in the washing machine.
Grey water is the effluent from a washing machine appliance that was used during a cycle in the washing machine. For example, grey water is created during a wash cycle. The water that is used for washing clothes or other articles will eventually come to contain e.g., detergent and other matter released from the clothes during the washing process. Grey water is also created during the rinse cycle. Water that is added to the clothes during the rinse cycle will also eventually contain e.g., detergent that is released during the rinse and/or spin process. If fabric softener is applied during the rinse cycle, then the grey water can also contain residual fabric softener as well as precipitates formed by the interaction of the detergent and fabric softener.
While grey water from a rinse cycle may be reused in a washing machine, the presence of fabric softener in such water can cause certain problems. Typically, the detergents that are used during the wash cycle of washing machine will contain surfactants. These surfactants affect the surface tension of the water and allow soil to be removed from the clothes, improve the wetting ability of the water, and help suspend soils in the water. Most commonly available laundry detergents use anionic type surfactants, which carry a negative charge. Commonly available fabric softeners also use surfactants, but their surfactants are cationic—i.e., carry a positive charge.
When a washing machine is operated with fabric softener, the fabric softener is typically added during the last rinse cycle. While a portion of the cationic surfactants of the fabric softener may be used during the rinse cycle, some will likely remain in the water at the end of the cycle. Accordingly, if grey water from the rinse cycle is to be reused in the washing machine, it is preferable that the cationic surfactants present in the grey water are not mixed with anionic surfactants from the detergent. Such mixing of the two differently charged surfactants can reduce the cleaning effectiveness of the detergent and form unwanted precipitates in the water, which in turn can form a residue on the articles being washed and the components of the washing machine.
Accordingly, a washing machine that can reuse grey water would be beneficial. More particularly, a washing machine that can reuse effluent or grey water from the rinse cycle, which may contain fabric softener, would be useful. Such a washing machine that can also determine whether fabric softener is present in the grey water from a rinse cycle would also be beneficial.